Question: Simplify the expression. $(-n^{4}-7n)(-7n^{3}-3n^{2}-7n)$
Explanation: First use the distributive property. $ - n^4 (-7 n^3) - n^4 (-3 n^2) - n^4 (-7 n) - 7 n (-7 n^3) - 7 n (-3 n^2) - 7 n (-7 n) $ Simplify. $7n^{7}+3n^{6}+7n^{5}+49n^{4}+21n^{3}+49n^{2}$